Fluctuation-Enhanced chemical and biological Sensing (FES) is known in the prior art. FES can be based on stochastic analysis and simulation and utilizes the stochastic component of sensor signals that can be caused by the statistical interaction between the sample being tested and the sensor. A typical FES system utilizes specially designed sensors, advanced signal processing and pattern recognition algorithms to measure electrical fluctuations in the sample, which can be caused by ion release due to disintegration and/or dissolution of bacteria during an induced phage infestation.
Many prior art FES methods for detecting and identifying bacteria are based on the detection and analysis of direct current (DC) voltage fluctuations, which are caused by the stochastic emission of ions during phage infection of a sample. For these systems and methods, a two-electrode nano-well device can be immersed in the carrier fluid containing a phage-infected sample and the microscopic voltage fluctuations are measured across the electrodes.
However, prior art methods that measure DC voltage fluctuations can have some fairly significant disadvantages. More specifically, these methods have not been shown to work for small bacterium numbers; all experiments so far used large samples (typically on the order of 10 million bacteria per sample). This can be because these techniques measure fluctuations in the DC electrical field; i.e., the underlying and assumed phenomenon can be the separation of positive and negative ions. Second, prior art DC FES system sensitivities can be limited by the presence of strong 1/f background noise (pink noise). Additionally, drift, aging of the electrode material and dependence on surface effects and corrosion can further degrade the performance of these types of systems.
In view of the above, it can be an object of the present invention to provide systems and methods for detecting and identifying bacteria in a sample by measuring impedance fluctuations due to phage infestation of the sample. Still another object of the present invention is to provide a bacteria identification by phage induced impedance fluctuation (BIPIF) analysis method with a much faster response time than the measuring methods of the prior art. Yet another object of the present invention is to provide BIPIF methods that can measure bacteria in a sample before the lysis of the bacteria by the phage that has been introduced into the sample. Still another object of the present invention is to provide a BIPIF methods with a sensitivity that is below the pink noise thresholds of direct current (DC) systems in the prior art. Another object of the present invention can be to provide systems and methods for detecting and identifying bacteria in a sample that offers several orders of magnitude improvement in sensitivity and higher reproducibility, at the expense of somewhat more sophisticated sensor circuitry and signal processing algorithms. Yet another object of the present invention can be to provide systems and methods for detecting and identifying bacteria in a sample that use alternating current (AC) impedance, so that the systems and methods work even when the negative and positive ions in the sample are in balance. Still another object of the present invention can be to provide systems and methods for detecting and identifying bacteria in a sample that increases detection sensitivity by minimizing the effect of noise sources such as 1/f noise, thermal noise and amplifier noise.